This invention relates generally to Intelligent Electronic Devices (IEDs) suitable for power system protection, control, monitoring and/or automation, and more particularly, to IEDs configured to facilitate communication within a group of compatible devices.
Various known electric power systems are spread over large geographical areas. These systems span from power generating stations through extra high voltage transmission facilities, to medium voltage distribution networks and electric loads. Components in such systems are constantly monitored by a plurality of devices to ensure continuous delivery of electric power. Known monitoring devices perform functions such as protection of assets, system protection, control, monitoring, recording, and/or metering. For example, a monitoring device may:
initiate the disconnection of an asset in case of an internal failure or of system conditions that jeopardize the asset,
initiate a disconnect of loads and/or generators to protect the integrity of the power system as a whole,
initiate an adjustment of parameters of processes for optimum operation of an asset or the power system as a whole,
measure and/or store an indication of system operating parameters, and/or signal an alarm with respect thereto,
produce a time record of system parameters for post-mortem analysis, and/or
measure parameters of the system for operation and/or revenue purposes.
Some of these monitoring devices have been developed using microprocessor-based technology, and are thus referred to herein as Intelligent Electronic Devices, or IEDs.
In the past few years, microprocessor-based protection and control devices as well as instrument transformers from which the protection and control devices get their key inputs have been developed that work with power system signals in the form of digital data packets exchanged over communication channels. Such communication channels include, for example, direct point-to-point fiber optic connections, optical or electrical based Ethernet, and optical or electrical serial ports. Data exchanged between IEDs (peer-to-peer) and IEDs and higher order systems such as Supervisory Control and Data Acquisition (SCADA) systems include status (on/off, healthy/faulty, enabled/disabled, etc.), metered values (voltage, current, power, frequency, temperature), sampled values (instantaneous currents and voltages), records (oscillographic files, logs, etc.), set-points and other data controlling operation of the devices (setting files, firmware/executable files), commands (open/close, etc.), and other.
Data sharing is provided between a plurality of monitoring devices can provide flexible and efficient communication. For example, data can be multiplexed on a common physical channel such as a copper wire. As another example, an external device can be used to physically separate communicating devices while moving buffered data between any two of the devices and redirecting data packets between an originating device and a destination device(s).
In at least one known configuration of a communication system for protection, automation or control and referring to prior art FIG. 1, an external communication switch enables communication between IEDs in a network 40. The physical media 30, 31, 32, 33 used is fiber optic or copper wire. IED 10 comprises a communication port 20 and uses a connection 30 to connect to a communication exchanger 14. IED 11 comprises a communication port 21 and uses a connection 31 to connect to communication exchanger 14. IED 12 comprises a communication port 22 and uses a connection 32 to connect to communication exchanger 14. IED 13 comprises a communication port 23 and uses a connection 33 to connect to communication exchanger 14. Additional communication ports 35 may be available to connect more devices. Connection to a network of devices is possible using communication port 34.
The use of the Ethernet standard and the IP protocol to transfer and share data between protective relays and/or IEDs has spread in the field of protection, automation and control. Communication switching devices (“switches”) have impact on the reliability and the cost of the system. The use of a switch such as communication exchanger 14 increases the cost and complexity of the network and reduces reliability unless single points of failure are eliminated by duplicating the entire communication network, which would increase the cost and complexity of the network even further.